Preprints
https://doi.org/10.5194/nhess-2022-1
https://doi.org/10.5194/nhess-2022-1
 
13 Jan 2022
13 Jan 2022
Status: a revised version of this preprint is currently under review for the journal NHESS.

Fault slip potential induced by fluid injection in the Matouying EGS field, Tangshan seismic region, North China

Chengjun Feng1,2, Guangliang Gao3,4, Shihuai Zhang5, Dongsheng Sun1,2, Siyu Zhu1, Chengxuan Tan1,2, and Xiaodong Ma5 Chengjun Feng et al.
  • 1Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing, 100081, China
  • 2Key Laboratory of Active Tectonics and Geological Safety, Ministry of Natural Resources, Beijing, 100081, China
  • 3China University of Petroleum, Qingdao, 266580, China
  • 4Jidong Oilfield Company, PetroChina, Tangshan, 063000, China
  • 5Department of Earth Sciences, ETH Zürich, Zürich, 8092, Switzerland

Abstract. The Tangshan region is one of the most seismically active areas in the North China, and the 1976 M 7.8 earthquake occurred on July 28th near the Tangshan fault zone. The Matouying Enhanced Geothermal Systems (EGS) field is located ~90 km away from Tangshan City. Since the late 2020, preliminary hydraulic stimulation tests have been conducted at depths of ~3965–4000 m. Fluid injection into geothermal reservoir facilitates heat exchanger system. However, fluid injection may also induce earthquakes. In anticipation of the EGS operation at the Matouying uplift, it is essential to assess how the fault slip potential of the nearby active and quiescent faults will change in the presence of fluid injection. In this study, we first characterize the ambient stress field in the Tangshan region by performing stress tensor inversions using 98 focal mechanism data (ML ≥ 2.5). Then, we estimate the principal stress magnitudes near the Matouying EGS field by analyzing in situ stress measurements at shallow depths (~600–1000 m). According to these data, we perform a quantitative risk assessment using the Mohr-Coulomb framework in order to evaluate how the main active faults might respond to hypothetical injected-related pore pressure increases due to the upcoming EGS production. Our results mainly show that most earthquakes in the Tangshan seismic region have occurred on the faults that have relatively high fault slip potential in the present ambient stress field. At well distances of less than 15 km, the probabilistic fault slip potential on most of the boundary faults increase with continuing fluid injection over time, especially on these faults with well distances of ~6–10 km. The probabilistic fault slip potential increases linearly with the fluid injection rate. However, the FSP values decrease exponentially with increased unit permeability. The case study of the Matouying EGS field has important implications for the deep geothermal exploitation in China, especially for Gonghe EGS (in Qinghai province) and Xiong’an New Area (in Hebei province) geothermal reservoirs that are close to the Quaternary active faults. Ongoing injection operations in the regions should be conducted with these understandings in mind.

Chengjun Feng et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on nhess-2022-1', Anonymous Referee #1, 07 Feb 2022
    • AC2: 'Reply on RC1', Chengjun Feng, 15 Feb 2022
    • AC5: 'Reply on RC1', Chengjun Feng, 25 Feb 2022
  • RC2: 'Comment on nhess-2022-1', Anonymous Referee #2, 11 Feb 2022
    • AC1: 'Reply on RC2', Chengjun Feng, 15 Feb 2022
    • AC4: 'Reply on RC2', Chengjun Feng, 25 Feb 2022
  • RC3: 'Comment on nhess-2022-1', Anonymous Referee #3, 17 Feb 2022
    • AC3: 'Reply on RC3', Chengjun Feng, 23 Feb 2022

Chengjun Feng et al.

Chengjun Feng et al.

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Short summary
We show how the FSP software package can be used as a quantitative screening tool to estimate the fault slip potential in a region with some uncertainties of the ambient stress field, and to assess the reactivation potential on these faults of presumably higher criticality in response to fluid injection. The case study of the MTY EGS field has important implications for the deep geothermal exploitation in China, especially for Gonghe Enhanced Geothermal Systems (EGS) in Qinghai province.
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